When driving smaller boats, in particular at difficult conditions the driver is exposed to great physical strains. The boat is tossed about and beats hard against the waves and the driver is jerked along. This is perhaps particularly marked for planing boats which are driven in hard weather and rough sea such as for example sea rescue boats on rescue tasks but this is also a problem when it concerns racing boats and rapid pleasure boats. The jerks result in that the driver has difficulties to keep full control of the boat simultaneously as the body is exposed to injury risks. A complex moving pattern arises in these situations in which the driver is exposed to rocking, rolling, heaving, jerks and vibrations, all in an unpredictable way. If the driver sits in a common boat seat behind a steering-wheel the back in particular is exposed to heavy torques and not seldom injuries occur in the spine as a result. These risks should it possible be minimized.